L9958 datasheet(12/38 Pages) STMICROELECTRONICS

12 / 38 page

Device description

L9958

12/38

Doc ID 17269 Rev 5

3.3

Serial peripheral interface (SPI)

The SPI is used for bidirectional communication with a control unit, allowing IC

configuration, diagnosis and identification. L9958 can also be used in daisy-chain

configuration (number of device in the daisy chain is not limited).

The SPI interface of L9958 is a slave SPI interface: the master is the µC which provides CS

and SCK to L9958.

Transfer format uses 16 bits word in case of single device configuration and multiple of 16

bits word in case of daisy chain configuration.

The first answer after Power-ON-Reset is the IC identifier.

A command sent by the µC during transfer N is answered during transfer N+1. SO is

clocked on SCK rising edge. SI is sampled on falling edge. When CS = '1' and during power-

ON reset, SO is in tri-state. Otherwise, the SPI interface is always active.

Settings made by the SPI control word become active at the end of the SPI transmission

and remain valid until a different control word is transmitted or a power on reset occurs.

At each SPI transmission, the diagnosis bits as currently valid in the error logic are

transmitted. Details on diagnosis are described in Section 5.

Figure 6.

SPI protocol structure

Between CS falling edge and SCK rising edge, an internal signal called "FSI bit" is set

asynchronously on SO output. This can be useful to have internal information on the device

without stimulating the SCK clock. The definition of the FSI bit is presented in the

diagnostics chapter.

Figure 7.

FSI bit

Except the Enable / Disable bit (“ACT” pin), all the bits of diagnosis register are latched and

can be released by:

●

Diagnosis register read by SPI

●

Power-On-Reset condition.

The coding for the Configuration and Diagnosis Registers is reported in the table below.

L9958 датащи(PDF) 12 Page - STMicroelectronics